The Ascent of Sap in Tall Trees: a Possible Role for Electrical Forces

Johnson B1*

1Independent Researcher, Oxford, UK

*Correspondence E-mail:

Key Words: Ascent of Sap, Multi-force Theory, Electrical Forces

Received May 6th, 2013; Accepted October 19th, 2013; Published November 3rd, 2013; Available online November 10th, 2013

doi: 10.14294/WATER.2013.9



The debate continues between proponents of the widely-accepted Cohesion-Tension Theory and those who consider that other forces, represented by the chemical potential equation, may also be involved in the ascent of sap. It has long been known that electrical potential differences exist in living trees but no viable mechanism has yet been proposed whereby these potential differences may help drive the flow in the xylem. More recently, it has been discovered that various mechanisms exist which can create large zones of charge separation in water. Combining these results here leads to a possible mechanism whereby the known electrical potential differences in trees could assist in driving sap flow. It is concluded that the electrical potential term in the water potential equation should be considered when investigating the range of possible forces involved in the ascent of sap. The role of the natural vertical electric field of the Earth is discussed in relation to generation of the observed potentials in living trees and various corollaries of the inclusion of electrical forces are suggested.

“The Cohesion – Tension Theory has prevailed largely unmodified for over 100 years, a somewhat unusual situation for a scientific paradigm explaining a fundamental process.” (Meinzer, Clearwater & Goldstein 2001, p243)

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